The Present Disclosure relates, generally, to a composite cable.
The ability to fold a casing, in order to both decrease the size of the overall case while increasing the size of a display, is emerging as a need for conventional electronic equipment. When doing so, a signal is transmitted by equipping a conductive wire, such as a flexible printed circuit (FPC), a narrow line coaxial cable or the like, so that it passes through the inside of a hinge part where a casing and another casing are connected, with the ability to rotate. In recent years, although high speed signal transmission is required for high definition images and the like, the restriction on the internal size of the hinge has made equipping a wide or large diameter conductive wire difficult. Further, when considering grounding measures to control electromagnetic interference (EMI), the width of the conductive wire becomes even larger.
In response to this, proposals have been made to integrate an optical waveguide with excellent EMI compatibility with a conductive wire to enable a large number of signals to be transmitted. An example of this is disclosed in Japanese Patent Application No. 2008-262244, the content of which is incorporated herein in its entirety.
FIG. 9 illustrates a conventional cable in which a conductive wire is integrated with an optical waveguide. A cable 901 includes a conductive film 950 with a stacked two layer structure provided on an optical waveguide film 910. The optical waveguide film 910 is a long and thin elastic band-shaped film and includes a plurality of mutually-parallel optical waveguide cores 911. Further, the conductive film 950 is also a long and thin band-shaped film that provides flexibility, and a plurality of conductive wires 951 are formed on the upper surface.
Further, the optical waveguide film 910 and the conductive film 950 are mutually bonded by an adhesive layer 941 at the end parts on both sides in the lengthwise direction of the cable 901. The end part of cable 901 is connected onto a circuit board (not shown), and one end of the conductive wire connected to an electronic device or the like on a circuit board is connected to the conductive wire 951 of the conductive film 950. Further, the optical waveguide core 911 of the optical waveguide film 910 is optically coupled to an optical element or the like (not shown).
Note that the optical waveguide film 910 and the conductive film 950 are not mutually adhered together, but are separate at the parts other than the cable 901 end part. Therefore, the cable 901 can bend freely at the parts other than the end part and can be housed in a bent state within, for example, the casing of an electronic device and can be wound in a spiral fashion in the hinge part that connects the two casings. However, with the conventional cable 901, because the flexible optical waveguide film 910 and the conductive film 950 are layered via a pliable adhesive layer 941, the flexibility is high, making it difficult to electrically connect the components such as an IC chip, chip condenser and the like to the conductive wire 951.
In general, when electrically connecting components such as an IC chip that is susceptible to heat to a substrate or the like, instead of using reflow soldering that requires heating, a technique for ultrasonic bonding is adopted for the connection that applies an ultrasonic wave to fuse a metal bump, such as a gold bump, formed on a terminal or the like. In addition, with ultrasonic bonding, an ultrasonic horn which is a tool for transferring ultrasonic waves is pressed to a component or a terminal of a component to apply an ultrasonic wave to a metal bump.
Thus, in order to connect a component to the conductive wire 951 of the conductive film 950 by ultrasonic bonding, it ultrasonic wave is applied by pressing the ultrasonic horn to the component mounted on the conductive film 950, but because the cable 901 below the component is flexible, the ultrasonic wave can escape by passing through the flexible cable 901 even when, for example, holding the opposite side of the cable 901 against the surface of a workbench with high rigidity, and therefore, a sufficient ultrasonic wave cannot be applied to the metal bump and the component cannot be reliably connected to the conductive wire 951.